posted April 26, 2001 11:58 AM

Hi, okay the calcs (I use english units) for a tire Overall Diameter: width in mm/25.4= width in inches. Width in inches x aspect ratio expressed as a decimal ie: 60 is .60) equals the height of your rubber above the rim(your sidewall) Multiply that times 2, add the rim diameter. this is the OD. For your 225/60R 16:225/25.4 x .60 x 2 + 16 = 26.63" overall.

Switching to a 235 60 R 16 (recommended!) amounts to an almost negligible increase in height-

235/25.4 x .60 x 2 + 16 = 27.10" overall

BECAUSE, remember, you mount a wheel in its center, your wheel wells, your ground clearance, your everything 'sees' 1/2 the diametral increase, ie the radial increase- which measures out to just .235" larger than your OE tires (a little bit more than a quarter inch...) Bear in mind, your current tires are probably (due to wear) that amount SMALLER than they are supposed to be, so you in effect have the current 'error' in speedo, in ABS, etc- already (only in the low side) than you'll have on the upside with the 235s. What I'm saying, if the car works properly now with 'undersized' worn tires, it'll work with .235" 'oversized' ones. This fact escapes the tire sales people, consistently.... i have oversized EVERY car I've owned by on average one aspect ratio (and same or 1-up in width, also) and have been thrilled with the results each time... The factory, OE tires are definitely a compromise solution, not optimized for ANYBODY.

quote:

Originally posted by as_soft:

**Hi**I have a '93 LS 400 with 4 Goodyear 225/60 /16 that came on the car.

What tires should I replace them with

235/60, 235/55, 245/55 - / 16

I live in NJ therefore I need all weather tires

I'm wondering if anyone could give me the formula to calculate the diameter or/and the circumference of the tire

Thanking you in advance for your help

**Ari**